1. Field of the Invention
This invention relates to a socket component for a female snap which, together with a male snap, constitutes a snap fastener, and more particularly to a plastic socket component having a cavity for coupling and uncoupling with a projection of the male snap and an opening defined centrally of a bottom wall of the cavity to receive a projection of a rivet driven in from one face of a flexible sheet to form a calking stop.
2. Description of the Prior Art
A known plastic socket component of the type described above is shown in FIG. 7. In this socket component 3' a cavity 10' is surrounded by a peripheral wall 13' having a substantial inverted U-shaped section and comprising an annular inner wall portion 13a' upstanding from the periphery of a bottom wall 11', an annular upper wall portion 13b' extending outwardly from the top of the inner wall portion 13a' and an annular outer wall portion 13c' depending from the outer edge of the upper wall portion 13b'. When coupling a projection 8' of the male snap and the cavity 10', the projection 8' is pushed into the cavity 10' elastically deforming the upper wall portion 13b'. When the projection 8' is seated in the cavity 10', the projection is cramped by the inner wall portion 13a' under the elastic restoring force of the upper wall portion 13b'. This plastic socket component 3' has the following two advantages:
(1) A relatively broad annular top surface S1' is defined by the upper wall portion 13b' around the opening end of the cavity 10'. Therefore, when the projection 8' of the male snap is to be inserted into the cavity 10', a peripheral portion of the projection 8' can be placed in contact with the annular top surface portion S1' and then guided into the cavity 10' by sliding over the annular top surface S1'. Thus positional adjustment between the projection 8' and the cavity 10' is achieved with ease.
(2) After a projection 4a' of a rivet 4' driven in from one face of a flexible sheet 5b' penetrates through an opening 12' defining centrally of the bottom wall 11' of the socket component 3' and the leading end of the projection 4a' is crushed to form a calking stop, the flexible sheet 5b' is held not only between the undersurface of the bottom wall 11' and the back face of a head 4b' of the rivet 4' but also between the undersurface of the outer wall portion 13c' located around the bottom wall 11' and the back face of the head 4b' of the rivet 4' opposed thereto. Therefore, the socket component 3' is secured to the flexible sheet 5b' in a reliable and stable manner.
However, the prior art construction described above has a disadvantage that the mating between the projection 8' and the cavity 10' becomes too loose or too tight depending on the thickness of the flexible sheet 5b'.
More particularly, where the flexible sheet 5b' comprises a thin material, the inner diameter at the opening end of the cavity 10' is maintained constant and therefore the projection 8' of the male snap can be fitted into the cavity 10' with a small force. On the other hand, where the flexible sheet 5b' comprises a thick material, the outer wall portion 13c' is pushed upward by the flexible sheet 5b' as seen in FIG. 7 when the flexible sheet 5b' is held between the undersurface of the outer wall portion 13c' and the back face of the head 4b' of the rivet 4'. The upper wall portion 13b ' then pushes the top of the inner wall portion 13a' toward the center of the cavity 10' reducing the inner diameter at the opening end of the cavity 10', which tends to result in difficulty in inserting the projection 8' of the male snap into the cavity 10'.
Furthermore, since an annular groove a is defined between the inner wall portion 13a' and the outer wall portion 13c' with the upper wall portion 13b' forming its bottom, water tends to remain in the groove a after the garment carrying the snap fastener is washed. As a result, the plastic material in the inside faces of the annular groove a absorbs the water to get distended and reduce the inner diameter at the opening end of the cavity 10', whereby the coupling between the projection 8' and the cavity 10' temporarily becomes too tight until the absorbed water fully dries up.